Steps to reproduce:
1) Open the latest attached project.
2) Build the project and deploy it to an iOS device.

When the app launches, a looping sound starts playing. The duration of the loop is twice as long as in the Editor (when the sound finishes playing no sound is played for the same duration as the length of the audio clip). The sound file if downloaded to the device using UnityWebRequest and stored in a persistent path.

Reproduced on:
5.5.0a5, 5.4.0f3

Devices tested:
iPhone 6+, 8.0
iPad Mini 2, 9.3.1